The present invention relates to an aerostatic bearing and to a method for producing micro holes which is especially applicable to the production of the aerostatic bearing.
Aerostatic bearings are based on air or another gas being blown in between two bearing bodies. The resulting dynamic pressure means that a gap is produced between the two bearing bodies, i.e. direct contact between the bearing bodies is avoided. It is thus possible to carry out relative movements between the bearing bodies with low frictional forces and thereby to realize a low-wear bearing with high efficiency. A supply channel for feeding the air or another gas into the bearing gap runs through one of the two bearing bodies, referred to below as the guide element. To maintain the gas cushion between the bearing bodies work must continuously be done. To keep the gas consumption—and thereby the energy consumption—of the bearing low or to achieve a high bearing force of the bearing, this supply is generally designed so that nozzles of the supply channel in a surface of the guide element facing towards the other bearing body, referred to below as the bearing surface, are arranged facing one another and represent the narrowest point of the supply.
An aerostatic bearing is known from DE 44 36 156 C1, of which the nozzles are micro holes created by laser radiation. The micro holes have a conical cross section, with the narrowest cross section of the nozzles lying directly adjacent to the bearing surface. Because of the conical cross-sectional shape the amount of material to be removed to produce the micro holes does not increase linearly with the width of the guide element but in a power-of-three relationship. Accordingly the processing time required for creating the micro holes also increases to the power of three of the width. The method is thus essentially only able to be used cost effectively for small widths of the guide element. Accordingly the figures of DE 44 36 156 C1 show wall widths which approximately correspond to the hole diameter.
A further problem of the conical hole shape is that, with a bearing under a heavy load, the bearing plate has have a high wall thickness to be sufficiently stable in shape. To safely avoid the bearing bodies coming into contact however, a high density of nozzles is simultaneously needed, which, as a result of their conical form, greatly weaken the bearing plate or restrict the maximum wall width able to be realized.
A further disadvantage of an aerostatic bearing with the conical nozzle geometry known from DE 44 36 156 C1 emerges from the fact that the gas throughput through a nozzle is uniquely defined by the pressure difference present at the nozzle and by the nozzle cross section. A minimum outlet cross section of the nozzle is predetermined by the parameters of the laser beam used for drilling the hole. If the position and the number of nozzles is also predetermined in the design of the bearing, this results in a gas consumption of the bearing which can no longer be exceeded during operation and which predetermines an upper limit for the efficiency of a linear compressor able to be realized with the aerostatic bearing.